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The interaction of lead (Pb) with plant hormonal balance and oxidative stress remains under discussion. To evaluate how Pb induces oxidative stress, and modulates the antioxidant enzymes and the phytohormones pool, four-week old Pisum sativum plants were exposed during 28 days to 10, 100 and 500 mg kg -1 Pb in soil. In comparison to leaves, roots showed higher Pb accumulation, oxidative damages and changes in phytohormone pools. Contrarily to leaves, where glutathione reductase (GR) and ascorbate peroxidase (APX) activities were more stimulated than catalase (CAT) and superoxide dismutase (SOD), roots showed a stimulation of SOD, GR and APX in all doses, and of CAT in the highest dose. While protein oxidation occurred in roots even at lower Pb-doses, lipid peroxidation and membrane permeability also occurred but at 500 mg kg -1 and in both organs, accompanied by increases of H 2 O 2 . Jasmonic acid (JA) responded in both organs even at lowest Pb-doses, while salicylic acid (SA) and abscisic acid (ABA, only in leaves), increased particularly at the concentration of 500 mg Pb kg -1 . In conclusion, and compared with leaves, roots showed oxidative damage even at 10 mg Pb Kg -1 , being proteins a first oxidative-target, although there is a stimulation of the antioxidant enzymes. Also, JA is mobilized prior to oxidative stress changes are detected, and may play a protective role (activating antioxidant enzymes), while the mobilization of SA is particularly relevant in cells expressing oxidative damage. Other hormones, like indolacetic acid and ABA may have a low protective role against Pb toxicity., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Olive leaves are an abundant by-product of olive oil production. Olive leaf extracts (OLEs) are rich in polyphenols, which can be used for health benefits. As polyphenols are the main antioxidant molecules in plants, plants typically increase their polyphenol content when exposed to drought stress. However, the phenolic profile of OLEs can vary in relation to the origin and variety of the plant material. In this work, olive leaf extracts from three different Italian olive cultivars (Giarraffa, Leccino, and Maurino) both exposed and not exposed to drought stress were studied in terms of antioxidant properties and profile, intestinal permeation, and protection against oxidative stress of human umbilical vein endothelial cells (HUVECs), since HUVECs are considered a model to study a wide range of diseases. OLEs from stressed Maurino and Giarraffa plants showed the highest increase in antioxidant capacity compared to controls. The phenolic profile of Maurino' was mainly increased by water deficit, with a large increase in the compounds oleuropein and luteolin-7-O-rutinoside. All tested extracts exposed to a water deficit protected HUVECs against oxidative stress by reducing ROS production, and this effect was more pronounced in OLEs from Giarraffa and Maurino exposed to drought stress compared to all other extracts. Finally, OLE from the stressed Giarraffa group showed a higher apparent permeability of antioxidant molecules than that of Maurino. [ABSTRACT FROM AUTHOR]

Cork oak (Quercus suber) is a species native to Mediterranean areas and its adaptation to the increasingly prevalent abiotic stresses, such as soil salinization, remain unknown. In sequence with recent studies on salt stress response in the leaf, it is fundamental to uncover the plasticity of roots directly exposed to high salinity to better understand how Q. suber copes with salt stress. In the present study we aimed to unveil the antioxidants and key-genes involved in the stress-responses (early vs. later responses) of Q. suber roots exposed to high salinity. Two-month-old Q. suber plants were watered with 300 mM NaCl solution and enzymatic and non-enzymatic antioxidants, lipid peroxidation and the relative expression of genes related to stress response were analysed 8 h and 6 days after salt treatment. After an 8 h of exposure, roots activated the expression of QsLTI30 and QsFAD7 genes involved in stress membrane protection, and QsRAV1 and QsCZF1 genes involved in tolerance and adaptation. As a result of the continued salinity stress (6 days), lipid peroxidation increased, which was associated with an upregulation of QsLTI30 gene. Moreover, other protective mechanisms were activated, such as the upregulation of genes related to antioxidant status, QsCSD1 and QsAPX2, and the increase of the antioxidant enzyme activities of superoxide dismutase, catalase, and ascorbate peroxidase, concomitantly with total antioxidant activity and phenols. These data suggest a response dependent on the time of salinity exposure, leading Q. suber roots to adopt protective complementary strategies to deal with salt stress. [ABSTRACT FROM AUTHOR]

Climate change scenarios increase the frequency of combined episodes of drought, heat and high UV radiation, particularly in the Mediterranean region where dryland farming of olive (Olea europaea L.) orchards remains a common practice. Nonirrigated olive plants (drought treatment) were subjected to an episode of heat plus UV-B radiation shock (DH+UV-B treatment) for 2 days. After the treatments, plants were allowed to grow under irrigated conditions (recovery). Compared with irrigated plants, drought treatment induced lower relative water content but this status was not aggravated when DH+UV-B shock was applied. Additionally, the effective quantum yield of PSII was similar in the drought-stressed and DH+UV-B treatments. Interestingly, the DH+UV-B treatment produced higher photosynthetic pigment contents than drought-stressed plants. Concerning oxidative status, the DH+UV-B treatment induced similar lipid peroxidation levels and only cell membrane permeability was higher than in drought-stressed plants. On other hand, drought-stressed plants showed higher levels of anthocyanins and proline. Our data suggest that plants grown under dryland conditions modulated some tolerance mechanisms that may prevent cumulative damages by other stressors. Moreover, drought-stressed and DH+UV-B plants were able to recover their physiological performance in a similar way. These data represent an important contribution to understanding how dryland -grown olive plants will cope with climate change. Climate changes are increasing the frequency of crop stress events, particularly in the Mediterranean region where dryland olive farming remains a sustainable practice. We aimed to evaluate how olive plants under irrigated versus dryland farming regimes respond to heat plus high UV-B, and recover. The results suggest that plants pre-exposed to drought can modulate tolerance mechanisms towards coping with further multiple stress episodes and recovery. [ABSTRACT FROM AUTHOR]

Chromium (Cr) contamination in arable soils and irrigating water remains a priority, particularly due to the challenges posed to crop production and food safety. Long-term Cr(VI) effects remain less addressed than short-term ones, particularly regarding organ-specific genotoxic profiles. Here we used the crop Lactuca sativa growing in a protected horticultural system and irrigated for 21 days with Cr(VI) (up to 200 mg/L). Besides the oxidative stress, the genotoxicity was evaluated. Shoots and roots showed distinctive oxidative stress status and genotoxic effects, in a dose-dependent manner. While 50 mg/L stimulated antioxidant activities and no major genotoxic effects were found, plants exposed to ≥150 showed an increase of oxidative disorders, together with cytostatic and DNA damage effects, and some mitotic impairment. Leaves showed less oxidative signs at 50 mg/L, while at 150/200 mg/L the antioxidant battery was stimulated. In Cr treated plants, the highest dose increased the DNA damage, reinforcing the idea that DNA breaks were related to mitotic disorders in higher doses. In conclusion, long-term exposure data show a highly responsive root, with a quadratic response meaning higher defenses at lower Cr doses, and higher oxidative and DNA damage and cytostatic effect at a higher dose. [ABSTRACT FROM AUTHOR]

Abstract: Candidate species for reforestation of areas prone to drought must combine water stress (WS) tolerance and economic or medicinal interest. Melia azedarach produces high quality timber and has insecticidal and medicinal properties. However, the impact of WS on M. azedarach has not yet been studied. Two-month old M. azedarach plants were exposed to WS during 20 days. After this period, plant's growth, water potential, photosynthetic performance and antioxidant capacity were evaluated. WS did not affect plants' growth, but induced stomatal closure, reduced net CO2 assimilation rate (A) and the intercellular CO2 availability in mesophyll (C i). WS also reduced the photosynthetic efficiency of PSII but not the pigment levels. WS up-regulated the antioxidant enzymes and stimulated the production of antioxidant metabolites, preventing lipid peroxidation. Therefore, despite some repression of photosynthetic parameters by WS, they did not compromise plant growth, and plants increased their antioxidant capacity. Our data demonstrate that M. azedarach juvenile plants have the potential to acclimate to water shortage conditions, opening new perspectives to the use of this species in reforestation/afforestation programs of drought prone areas. [Copyright &y& Elsevier]

Iron-magnetic nanoparticles (Fe-NMPs) are widely used in environmental remediation, while porphyrin-based hybrid materials anchored to silica-coated Fe 3 O 4 -nanoparticles (Fe 3 O 4 -NPs) have been used for water disinfection purposes. To assess their safety on plants, especially concerning potential environmental release, it was investigated for the first time, the impact on plants of a silica-coated Fe 3 O 4 -NPs bearing a porphyrinic formulation (FORM) - FORM@NMP. Additionally, FORM alone and the magnetic nanoparticles without FORM anchored (NH 2 @NMP) were used for comparison. Wheat (Triticum aestivum L.) was chosen as a model species and was subjected to three environmentally relevant doses during germination and tiller development through root application. Morphological, physiological, and metabolic parameters were assessed. Despite a modest biomass decrease and alterations in membrane properties, no major impairments in germination or seedling development were observed. During tiller phase, both Fe 3 O 4 -NPs increased leaf length, and photosynthesis exhibited varied impacts: both Fe 3 O 4 -NPs and FORM alone increased pigments; only Fe 3 O 4 -NPs promoted gas exchange; all treatments improved the photochemical phase. Regarding oxidative stress, lipid peroxidation decreased in FORM and FORM@NMP, yet with increased O 2 -• in FORM@NMP; total flavonoids decreased in NH 2 @NMP and antioxidant enzymes declined across all materials. Phenolic profiling revealed a generalized trend towards a decrease in flavones. In conclusion, these nanoparticles can modulate wheat physiology/metabolism without apparently inducing phytotoxicity at low doses and during short-time exposure. Iron-magnetic nanoparticles are widely used in environmental remediation and fertilization, besides of new applications continuously being developed, making them emerging contaminants. Soil is a major sink for these nanoparticles and their fate and potential environmental risks in ecosystems must be addressed to achieve more sustainable environmental applications. Furthermore, as the reuse of treated wastewater for agricultural irrigation is being claimed, it is of major importance to disclose the impact on crops of the nanoparticles used for wastewater decontamination, such as those proposed in this work. [Display omitted] • FORM@NMP promoted gas exchange and Φ PSII , and down regulated the antioxidant response. • NH 2 @NMP increased pigment levels, gas exchange, and Φ PSII. • FORM impaired seedling biomass, increased pigments and Φ PSII , and decreased MDA. • Flavone levels showed a generalized trend do be down regulated. [ABSTRACT FROM AUTHOR]

Climate change is increasing the frequency of heat waves accompanied by drought episodes. These challenges are increasing in the Mediterranean basin, where Olea europaea L. has an important ecological and economic role. Olive breeding programs have been focused on highly productive cultivars, while ancient cultivars may present higher tolerance to drought and heat resilience. Therefore, it is important to select traditional cultivars that may give reliable performances under the emerging climate change scenarios. In the present work, the differential physiological response of economically important traditional Portuguese olive cultivars, Cobrançosa, Cordovil de Castelo Branco (C.C. Branco), and Cordovil de Serpa (C. Serpa), to drought combined with heat are evaluated. Stress treatment had lowest impacts on water status in Cobrançosa. Also, this cultivar was less affected regarding pigments content, maximum and effective quantum yield of photosystem II (F v /F m and Φ PSII ) and exhibited higher ability to trigger an antioxidant response. C.C. Branco was the most sensitive cultivar in response to pigments (carotenoids), F v /F m and Φ PSII , and cell membrane stability. Principal component analysis suggested that Cobrançosa has high potential to withstand climate change events, particularly drought combined with heat episodes, followed by C. Serpa and C.C. Branco. [ABSTRACT FROM AUTHOR]

• TiO 2 -NP is toxic above 5 mg L−1, being wheat shoots more sensitive than roots. • Leaves triggered thiol and AsA metabolism to counteract TiO 2 -NP toxicity. • Roots preferred antioxidant route involves pre-existing antioxidant capacity. • The induced antioxidant mechanisms did not prevent cellular oxidation. • Biochemical and transcriptional gap responses suggest time-dependent adaptations. Nanoparticles (NP) bioactivity is under deep scrutiny. In this work, the antioxidant response to TiO 2 -NP in wheat (Triticum aestivum) was determined. For that, enzymatic and the non-enzymatic antioxidants were evaluated in plants exposed to the P25 anatase:rutile material composed of TiO 2 -NP and under environmentally realistic doses (0; 5; 50; 150 mg/L for 20 days). Shoot but not root growth was reduced. In leaves, thiol metabolism and ascorbate accumulation were the preferred route whereas in roots the pre-existing antioxidant capacity was preferentially utilized. Both leaves and roots showed increased glutathione reductase and dehydroascorbate reductase activities and decreased ascorbate peroxidase activity. Roots, nevertheless, presented higher enzymatic basal levels than leaves. On the other hand, when examining non-enzymatic antioxidants, the ratio of reduced-to-oxidized glutathione (GSH/GSSG) increased in leaves and decreased in roots. Exposed leaves also presented higher total ascorbate accumulation compared to roots. TiO 2 -NP exposure down regulated, with more prominence in roots, antioxidant enzyme genes encoding catalase, ascorbate peroxidase, monodehydroascorbate reductase and dehydroascorbate reductase. In leaves, superoxide dismutase gene expression was increased. All data pinpoint to TiO 2 -NP toxicity above 5 mg/L, with aerial parts being more susceptible, which draws concerns on the safety doses for the use of these NPs in agricultural practices. [ABSTRACT FROM AUTHOR]

Climatic change challenges are predicted to increase combined episodes of drought, heat and higher UVB-radiation, which will impact crops/plants production. Moringa oleifera is a major source of food/economy in underdeveloped regions, and its tolerance to high UVB radiation (UVB) and water deficit (WD) remains unclear. We exposed two-month old plants to: a) WD for 4 days; b) UVB radiation for 3 days (26.3 kJ m − 2 ); c) WD + UVB in combination for 4 days (the UVB stress was imposed at the 2nd day of WD). One and ten days after the end of stresses the following parameters were measured: plant growth, water-status, chlorophyll a fluorescence, leaf gas-exchange, pigments, carbohydrates, cell-membrane-stability, phenols, malondialdehyde content and antioxidant capacity (including antioxidant enzymes). Stress exposure did not affect plant water status. One day after the end of the stresses, net CO 2 assimilation rate dropped in all treatments, but after 10 days an overall recovery was observed, except in plants exposed to UVB treatment. The plants exposed to UVB showed, in general, more severe effects, increasing pigment content and MDA, while no changes were observed in the total antioxidant capacity (after 1 day). Our data suggest that young M. oleifera plants present some tolerance to WD or UVB radiation and that the combination of the two stresses led to lower stressful responses than the UV stress imposition alone (photosynthesis, pigments, starch and antioxidant capacity). The lower outcome shown in the combined stresses suggest that this species is able to cope multiple stresses, and that a previous acclimation (possibly activating the antioxidant capacity) to one of the stresses may play an important role in this tolerance. [ABSTRACT FROM AUTHOR]